class Circle {
  //创建对象
  //以一个圆为对象
  //设置随机的 x，y坐标，r半径，_mx，_my移动的距离
  //this.r是创建圆的半径，参数越大半径越大
  //this._mx,this._my是移动的距离，参数越大移动
  constructor (x, y) {
    this.x = x
    this.y = y
    this.r = Math.random() * 10
    this._mx = Math.random()
    this._my = Math.random()

  }

  //canvas 画圆和画直线
  //画圆就是正常的用canvas画一个圆
  //画直线是两个圆连线，为了避免直线过多，给圆圈距离设置了一个值，距离很远的圆圈，就不做连线处理
  drawCircle (ctx) {
    ctx.beginPath()
    //arc() 方法使用一个中心点和半径，为一个画布的当前子路径添加一条弧。
    ctx.arc(this.x, this.y, this.r, 0, 360)
    ctx.closePath()
    ctx.fillStyle = 'rgba(204, 204, 204, 0.3)'
    ctx.fill()
  }

  drawLine (ctx, _circle) {
    let dx = this.x - _circle.x
    let dy = this.y - _circle.y
    let d = Math.sqrt(dx * dx + dy * dy)
    if (d < 150) {
      ctx.beginPath()
      //开始一条路径，移动到位置 this.x,this.y。创建到达位置 _circle.x,_circle.y 的一条线：
      ctx.moveTo(this.x, this.y)   //起始点
      ctx.lineTo(_circle.x, _circle.y)   //终点
      ctx.closePath()
      ctx.strokeStyle = 'rgba(204, 204, 204, 0.3)'
      ctx.stroke()
    }
  }

  // 圆圈移动
  // 圆圈移动的距离必须在屏幕范围内
  move (w, h) {
    this._mx = (this.x < w && this.x > 0) ? this._mx : (-this._mx)
    this._my = (this.y < h && this.y > 0) ? this._my : (-this._my)
    this.x += this._mx / 2
    this.y += this._my / 2
  }
}

//鼠标点画圆闪烁变动
class currentCirle extends Circle {
  constructor (x, y) {
    super(x, y)
  }

  drawCircle (ctx) {
    ctx.beginPath()
    //注释内容为鼠标焦点的地方圆圈半径变化
    //this.r = (this.r < 14 && this.r > 1) ? this.r + (Math.random() * 2 - 1) : 2;
    this.r = 8
    ctx.arc(this.x, this.y, this.r, 0, 360)
    ctx.closePath()
    //ctx.fillStyle = 'rgba(0,0,0,' + (parseInt(Math.random() * 100) / 100) + ')'
    ctx.fillStyle = 'rgba(255, 77, 54, 0.6)'
    ctx.fill()

  }
}

//更新页面用requestAnimationFrame替代setTimeout
window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame

let canvas = document.getElementById('canvas')
let ctx = canvas.getContext('2d')
let w = canvas.width = canvas.offsetWidth
let h = canvas.height = canvas.offsetHeight
let circles = []
let current_circle = new currentCirle(0, 0)

let draw = function () {
  ctx.clearRect(0, 0, w, h)
  for (let i = 0; i < circles.length; i++) {
    circles[i].move(w, h)
    circles[i].drawCircle(ctx)
    for (j = i + 1; j < circles.length; j++) {
      circles[i].drawLine(ctx, circles[j])
    }
  }
  if (current_circle.x) {
    current_circle.drawCircle(ctx)
    for (var k = 1; k < circles.length; k++) {
      current_circle.drawLine(ctx, circles[k])
    }
  }
  requestAnimationFrame(draw)
}

let init = function (num) {
  for (var i = 0; i < num; i++) {
    circles.push(new Circle(Math.random() * w, Math.random() * h))
  }
  draw()
}
window.addEventListener('load', init(60))
window.onmousemove = function (e) {
  e = e || window.event
  current_circle.x = e.clientX
  current_circle.y = e.clientY
}
window.onmouseout = function () {
  current_circle.x = null
  current_circle.y = null

}
export { //很关键
  draw,init,Circle,currentCirle,
}